The present invention relates to an improvement of a sealing means disposed between the cylinder and the piston of a disk brake, which sealing means has well-known double functions, i.e., restoration to a certain to-be-retained position of the piston and the automatic adjustment of the brake clearance in the case of the pad wearing, while preserving the essential function of fluid tightness.
In conventional disk brakes the returned position of the brake has been apt to be influenced by the difference of the brake fluid pressure applied, resulting in so-called "drag" and/or difference of the fluid amount required for a successive brake action. Both drag and difference in fluid amount are distinct disadvantages.